There’s a number of factors that contribute to this.
1. Porky Pig Effect. Like Rick pointed out, the last time we saw Fido was just before the style change, in his vest. This is his first “revamped” appearance.
2. Proportions. Fido’s larger than Bino now, as opposed to being the same size as he (almost) was when he first appeared in the comic.
3. Rendition. Fido’s MUCH less of a cartoon character in this shot than Bino, and having them side by side only stresses that. Fido appears much more “realistic” than Bino – his build is much more defined, instead of the abstract cartoon characters tend to follow. Next to Bino, who’s very cartoonish in comparison, it stands out.

In all honesty, Fido may need more tweaking – try putting him in a shot with Peanut as an experiment (not a full strip per say, but a sketch), and see how that looks – he’s striking me more as a humanish dog (furry, anthro, ect, whatever term floats your boat) than a housepet – Peanut, Grape, and the others do exhibit a lot of human qualities, but they never hit you as being physically human – more like pets that walk on two legs. In this shot, Fido could have human-style legs and some hybrid of feet/paws, and I wouldn’t even blink. But neither would the typical “paws” the characters have had before – it’s a grey area if anything.

This is, of course, just a suggestion – they’re your characters, your comic, so your rules.

Like I said, “almost,” lol. Straighten Bino out in that comic, and Fido’s only just barely taller. Here, straighten Bino out (on another tangent, is it me, or is he always hunched over or something?), and Fido’s at least a head or two taller than him – about one and a half at least. Probably an effect of Fido standing straight, while Bino’s bent over from excitment and stark terror (they did light a house on fire after all…), but there’s a bigger difference than before.

… or for all we know, one of them is standing on the remains of that pulpit Bino read the rules from last Friday, lol. ; )

they’re dogs, without their owners watching them *facepalm*
sides, this isn’t even close to a serious comic 90% of the time, it’s like tom and jerry he always wound up in a cast or worse for the most part, but you’d never know it after it’s over.

also, the more i look, the more i doubt the third panel egg actually exists ;-P

It’s like the 4th panel egg – Bino ate that one, the 3rd one got crispified (hence “Third Cinder from the left…) XD

On a more serious note, it’s prolly there – there’s a vague yellow egg-shape there in the said spot – would make it hard to notice if the color saturation was off by only a shade or two from the flames. Either way, very clever, Rick – people will be looking for these “Easter” eggs for days.

I have to say i personally like the way Fido looks makes him look like he’s the brother that’s had to work out hard and keep in shape since he is a cop after all, and whats to say that he’s not just walking around with his shirt off. If he was built from having to do hard work i’d say he’d be proud of his body. All in all though, what did they do to start a fire and who’s house is that lol?